The present invention relates to control linkages and pertains particularly to a combined linkage for the combined and simultaneous control of an engine throttle and a transmission from a single foot pedal.
Many vehicles such as lift trucks and the like have article-handling implements mounted thereon. These implements are normally controlled by the operator simultaneously with control of the vehicle. It is frequently necessary that the operator be able to effectively manipulate the article-handling implements at the same time that he is effectively manipulating the vehicle.
The operator of a lift truck, for example, may raise or lower the article-handling implement at the same time that he is moving either forward or backward and at the same time that he is steering the vehicle. Such maneuvers normally require simultaneous use of both hands and both feet.
Many of these functions are frequently incorporated in foot pedals. The most desirable pedal configuration is to have only one direction input to a pedal. This, however, tends to require so many pedals or to cause clutter and confusion.
In order to make such vehicles more efficient and easier to operate, it is necessary to combine as many of the functions as possible. It is necessary, for example, to incorporate as many functions as possible in a single foot pedal. This is necessary because it is essential that one foot be available for operation of the creeper pedal of the vehicle.
Where such vehicles employ hydrostatic transmission, it is frequently feasible to combine the throttle control with the transmission control. This is possible where the speed control or ratio control of the vehicle employs a linkage which is operative to swivel the swash plate of the hydrostatic transmission from a zero to a forward or reverse position. It is also desirable, however, that both forward and reverse be incorporated in a single pedal in order to reduce the number of pedals necessary on the vehicle and also that the throttle be incorporated in the same pedals. It is also necessary that the throttle be operable independent of the shifting of the ratio of the vehicle, in order that power from the vehicle may be utilized for manipulating the article-handling implements at a time when the vehicle is stationary.
Rocker type pedals have been proposed in order to incorporate more functions in a single pedal. The rocker type pedal, however, requires an unnatural motion, and is awkward and tiresome to control.